Apparatus and method for injection and dissemination of dry fly ash in mine voids

ABSTRACT

A supplemental source of compressed air is introduced near the discharge end of a conduit introducing air entrained dry fly ash into a mine void, to maintain the free flow characteristic of a fly ash mixture for a greater time and distance than would be the case without such introduction of supplemental air. A diffuser is used to disseminate the supplemental air into a plurality of streams.

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United States Patent [151 3,684,022 Peterson 1 Aug. 15, 1972 [54]APPARATUS AND METHOD FOR 3,421,587 H1969 Heavilon et al 169/2 RINJECTION AND DISSEMINATION OF 3,500,934 3/1970 Magnuson ..169/2 R DRYFLY ASH IN MINE VOIDS Inventor: Carl A. Peterson, 153 W. Maple Pnma'yExammerflM' Henson wood Ave, Hershey, Dauphin County,

FLY ASH-AIR MIXTURE Assistant Examiner-Thomas C. Culp, .lr.

' Attorney-Frank J. Benasutti [57] ABSTRACT A supplemental source ofcompressed air is introduced near the discharge end of a conduitintroducing air entrained dry fly ash into a mine void, to

maintain the free flow characteristic of a fly ash mixture for a greatertime and distance than would be the case without such introduction ofsupplemental air. A diffuser is used to disseminate the supplemental airinto a plurality of streams.

12 Claims, 3 Drawing Figures PATENTEDAU: 15 I972 FLY ASH-AIR MIXTURECOMPRESSED AIR FQQ

INVENTOR Carl A. Peterson ATTORNEY.

APPARATUS AND METHOD FOR INJECTION AND DISSEMINATION OF DRY FLY ASII INMINE VOIDS BACKGROUND OF THE INVENTION This invention relates to animprovement in the presently used methods and apparatus for injectingand disseminating dry fly ash into mine voids through they are used. Forpurposes of simplicity in describing the present improvement, thedisclosures of these patents are incorporated herein by reference.Suffice it to say that the apparatus and methods previously used injectfly ash in a fluidized state, usually with compressed air, through apipe in a borehole into the'mine voids. Fluidization is accomplished byintroducing compressed air into a settled mass of dry fly ash usuallyfrom the underside. The particles of the fly ash are of such very smalldiameter and weight that upon introduction of compressed air by suitablemeans they are suspended in air and respond to a hindered settlingeffect as a result of the individual particles being separated andbounded by very thin films of air. The suspension of dry fly ash in airthus created, behaves in the manner of a fluid in that it flowslaterally and comes to rest only as the fly ash particles settle out ofsuspension. This requires a short period of time. The lateral movementof finely particulate matter by fluidization in air is not dependent onthe velocity of impact of the compressed air. The air may be injectedunder the fly ash in any direction including the vertical. A hydraulicanalogy to the suspension of dry fly ash in air would be quicksand,which is a suspension of sand in water and which flows in the manner ofa fluid.

By the methods heretofore used the dry fly ash and air comes down theborehole and the fly ash is deposited in the mine void directly underthe injection borehole; accumulating until it contacts the roof of themine void. Because of its finely particulate nature the fly ash flowsbut a short distance beyond the borehole in the ceiling of the mine voidand thus makes contact with the roof of the mine void after havingtravelled only a limited lateral distance.

SUMMARY OF THE INVENTION My invention is an improvement upon the priorart methods in that it provides a means for prolonging the fluidizedstate of a dry fly ash (or other finely particulate material) mixturethereby allowing it to travel laterally a greater distance than washeretofore possiblc. The effect is to cause the injection hole to accepta greated quantity of fly ash and make the fly ash seal or contact agreater area of the mine void than would be the case without the use ofmy invention. The apparatus and process in accordance with the presentinvention provides a means for introducing supplemental air at thedischarge end of the hole within the mine void while the dry fly ash isin a fluid state, and changing the direction of this fluid whilemaintaining it in a fluid state for a longer period of time. In the mostpreferred embodiment the supplemental air is introduced through adiffuser which breaks the air into a plurality of small streams forintroduction into the mainstream of fluidized dry fly ash.

Accordingly, it is an object of this invention to improve presentmethods of dry fly ash injection by providing a means for prolonging thefluidization of the dry fly ash after discharge from the injection meansin mine voids.

This, and other objects of my. invention, will become apparent from thefollowing description with reference to the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a foreshortened verticalsectional view partially broken away showing the overall arrangement forthe introduction of dry fly ash into a mine void in accordance with thepreferred embodiment of my invention;

FIG. 2 is a greatly enlarged plan view of the diffuser portion of theapparatus taken as indicated by lines and arrows 2-2 in FIG. 1; and

FIG.'3 is a section of the diffuser and its adjoining pipe taken asindicated by the lines and arrows 3-3 in FIG. 2.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Although specific forms of theinvention have been selected for illustration in the drawings and thefollowing description is drawn in specific terms for the purpose ofdescribing these forms of the invention, this description is notintended to limit the scope of the invention which is defined in theappended claims.

FIG. 1 shows a portion of a system for injecting fluidized dry fly ashinto a mine void. Reference is made to the previously mentioned U.S.patents for the details of the fly ash, fly ash container and method andapparatus for introducing it through the pipe into the mine void. Forpurposes of this application, I have shown a hole 10 (foreshortened)which extends from the ground surface 12 through the ground to the minevoid 14. Mounted within this hole is a pipe 16 supported by a flange 18or other suitable means well known in the art. The upper end of the pipeis con nected by means of a tee 20 to a flexible hose 22 whichintroduces the fly ash and air mixture from the container (not shown).The fly ash mixture proceeds down the pipe in a fluidized state and isejected at 24 into the mine void.

In accordance with the preferred embodiment of my invention air isintroduced at a point somewhat below the opening into the mine void.

The heighth of the mine void cavity may range from two or three feet totwelve feet or more. It is. desirable in accordance with my invention topermit the fluidized dry fly ash to enter the void and to introduce airinto it preferably while it is still in a fluidized state. Accordingly,the introduction of supplemental air must be at a point spaced below theopening into the mine void. For example, for a 12 foot high cavern theintroduction of air would be at about 3 to 5 feet below the opening inthe ceiling of the cavern.

The air is introduced through a perforated discshaped member 26 shown ingreater detail in FIGS. 2 and 3. The disc shown is cylindrical and madeof a metallic material and has perforations in both the radial surfacesat the top and bottom and the circumferential side surface. The diameterof the disc is less than the inside diameter of the pipe 16 so that thedisc can be readily inserted through the pipe into the cavern or minevoid. To give some idea of the dimensions involved, for a 8-inchborehole, a 6-inch pipe 16 could be used and the diffuser 26 could be 4inches in diameter. The diffuser hole proportions would be substantiallythose shown in FIGS. 2 and 3. The compressed air flexible hose 28 wouldbe on the order of one to two inches or larger as necessary and can bemade of a flexible material or one or more sections of rigid pipethreaded into the upper flange 30 (FIG. 3) of the diffuser 26.

The upper end of the hose 28 has a valve illustrated schematically at 32in FIG. 1 for regulating the compressed air from a source not shown. Itis, of course,

possible to use the same compressed air source as is used in furnishingthe air to the dry fly ash mixture initially, by any suitable valving aswould be well known in the art. The pressure can then be adjusted asdesired for operating conditions given the quantity of fly ash, thepressure at which it is introduced into the chamber, the length of thepipe and other factors well known in the art.

It will be appreciated by those skilled in the art that the pressure ofthe compressed air, introduced through the diffuser and the position ofthe diffuser should be adjusted to accommodate environmental conditionsand parameters well known in the art. Likewise, the diameter ofperforations in the diffuser should be controlled to accomplish thedesired distribution of air to all the perforations with a minimalfrictional resistance to the flow of air thereto. The perforations shownprovide separate and distinct air streams into the mixture coming downthe pipe 28 and being discharged at 24 into the cavern. These airstreamsunite with the discharged fluidized fly ash and prolong the fluidizationof the fly ash within its course of travel in the chamber. Thisprolongation is indicated by the outer truncated cone shown by the linesA--A. These lines illustrate the contact line of the settled fly ashwith the bottom and roof of the mine void when the perforated disc 26 isused in accordance with my invention. The diffusion of the fluidized flyash is shown by the arrows and scatter pattern illustrated in FIG. 1.

Without such a diffuser for the introduction of supplemental air at thedischarge into the mine void, the fly ash would settle out much faster,that is, it would not travel laterally as far, and the contact line ofthe settled fly ash with the roof and the floor of the mine voidwould-be much closer to the introduction of the fly ash, as illustratedby the truncated cone shown by the lines 8-8 in FIG. 1.

It is desirable to prevent channeling of airstreams through the fly ashand for this purpose I have made provision for a rotatable packing gland34 at the upper end of the tee through which the conduit 28 passes. Thisallows for rotation of the conduit supplying the air.

Any suitable means can be provided for adjusting the height of theconduit within the chamber such as, for instance, locking the upper endthereof in the packing gland 34.

l further contemplate using a pleated plastic or fabric bag or screenhaving perforations or meshes for the escape of air in place of therigid perforated disc 26. Alternatively, although less desirable, thesupplemental air supply 28 could terminate within the chamber without adiffuser so that air would escape freely and be introduced into the flyash mixture being introduced into the chamber.

Mine voids are generally connected with the outside atmosphere at moreor less distant points from the introduction of the fly ash mixture.These provide an alternate path for escape of entrained and supplementalair. Injection of dry fly ash through a borehole may progress to thestage of refusal, however, at which stage the settled fly ash (or otherparticulate matter) makes a seal or complete circumferential contactwith the roof of the mine void at some radius from the injection hole.The escape into the surrounding mine void of air in which the dry ash issuspended, is then cut off. To permit complete filling of the mine voidup to and into the injection borehole, I have provided an alternateescape path to the outside atmosphere for the entrained air. This path38 is between the pipe 16 and the borehole 10. A plurality of plugs 40are disposed through the plate 18 and these can be removed in order topermit the air to escape.

Alternatively, an alternate air escape path may be provided by an airescape borehole drilled adjacent to the injection borehole and nearenough to the holes entrance into the mine void to permit completefilling of the mine void. Of course, this is a more expensive procedureand is less desirable than providing a space between the standpipe 16and the initial borehole 10. Such an alternative hole is illustrated inFIG. 1 by the dash lines 42. The distance separating the injectionborehole and the air escape borehole should be the minimum distancepossible consistent with good drilling practice. A soil casing pipe (notshown) can be inserted into the air escape borehole which can then belightly capped at the surface until the refusal stage is reached; whichwill be signaled by an increase in the emission of air and dust from theair escape borehole. If the cap is screwed on tightly, a pressure gaugemay be attached through the air escape borehole cap or the injectionborehole plug to signal the build-up of back pressure indicating theapproaching refusal stage of the injection process. When the refusalstage is reached, the soil pipe can be removed or the plug 40 can beremoved permitting air to escape. As this stage is reached, it isdesirable to slowly remove the perforated disc by withdrawing the pipeor conduit 28.

Of course, as the precess of completing the filling of the mine voidnears termination, it is not necessary to continue to supplysupplemental air in order to prolong the fluidization process.Accordingly, the valve 32 can be closed and the pipe 28 removed allowingthe fluidized fly ash air mixture to fill the remaining hole.

As will be appreciated by those skilled in the art, within goodpractice, both the injection borehole and the air escape borehole areprovided with soil casing pipes which extend from the surface of theground through the soil and into the solid rock strata into which thepipes are securely embedded with grout of sufficient strength to resistleakage of the compressed air during the process. Further, suitable dustcollecting equipment (not shown) may be used as necessary.

It will be understood that various changes in the details, materials andarrangement of parts which have been herein described and illustrated inorder to explain the nature of this invention, may be made by thoseskilled in the art within the principle and scope of the invention asexpressed in the following claims.

For example, it should be possible within the scope of this invention touse nitrogen or other gasses or gas mixtures other than air and to useparticulate matter of a suitable size amenable to injection andfluidization, and further, to fill other voids and cavities or spacesother than mine voids.

The Abstract of the Disclosure." set forth above is intended to providea non-legal technical statement of the contents of the disclosure incompliance with the Rules of Practice of the United States PatentOffice, and is not intended to limit the scope of the inventiondescribed and claimed herein.

What is claimed is:

1. A process of introducing supplemental air into a chamber into whichfluidized particulate matter is being introduced, comprising the step ofintroducing compressed gas at a point spaced from the point at which thefluidized material is being introduced into the chamber and releasingthis compressed gas into the material as it enters the chamber whilesaid material is still in a fluidized state.

2. The invention of claim 1 with the additional step of diffusing thecompressed gas so introduced into said fluidized material.

3. The invention of claim 2 wherein said diffusion consists of dividingsaid compressed gas into a plurality of separate streams of gas prior tointroducing it into the fluidized material.

4. An apparatus for prolonging the fluidization of finely dividedparticulate matter being introduced into a chamber, comprising: meansfor introducing a supplemental supply of compressed gas into thefluidized matter after its entry into the chamber while it is still influid state.

5. The invention of claim 4 wherein said means comprises a supplementalsource of compressed gas, and conduit means connected at one end to saidsource and having an outlet at another end within said chamber.

6. The invention of claim 5 wherein said conduit terminates in adiffuser within said chamber.

7. The invention of claim 6 where said diffuser comprises a disc havinga plurality of perforations therein.

8. The invention of claim 6 wherein 'said diffuser comprises a means fordividing the compressed gas into a plurality of separate streams.

9. The invention of claim 5 wherein said conduit passes through a pipe,said pipe providing the means for introducing said particulate matterinto said chamber.

10. The invention of claim 6 wherein said diffuser is spaced below theentrance of the fluidized particulate matter in said chamber.

11. Invention of claim 5 wherein said outlet is rotatable within saidchamber.

12. Invention of claim 4 wherein additional means are provided connectedto said chamber for exhausting the supplemental supply of compressed gastherefrom.

1. A process of introducing supplemental air into a chamber into whichfluidized particulate matter is being introduced, comprising the step ofintroducing compressed gas at a point spaced from the point at which thefluidized material is being introduced into the chamber and releasingthis compressed gas into the material as it enters the chamber whilesaid material is still in a fluidized state.
 2. The invention of claim 1with the additional step of diffusing the compressed gas so introducedinto said fluidized material.
 3. The invention of claim 2 wherein saiddiffusion consists of dividing said compressed gas into a plurality ofseparate streams of gas prior to introducing it into the fluidizeDmaterial.
 4. An apparatus for prolonging the fluidization of finelydivided particulate matter being introduced into a chamber, comprising:means for introducing a supplemental supply of compressed gas into thefluidized matter after its entry into the chamber while it is still influid state.
 5. The invention of claim 4 wherein said means comprises asupplemental source of compressed gas, and conduit means connected atone end to said source and having an outlet at another end within saidchamber.
 6. The invention of claim 5 wherein said conduit terminates ina diffuser within said chamber.
 7. The invention of claim 6 where saiddiffuser comprises a disc having a plurality of perforations therein. 8.The invention of claim 6 wherein said diffuser comprises a means fordividing the compressed gas into a plurality of separate streams.
 9. Theinvention of claim 5 wherein said conduit passes through a pipe, saidpipe providing the means for introducing said particulate matter intosaid chamber.
 10. The invention of claim 6 wherein said diffuser isspaced below the entrance of the fluidized particulate matter in saidchamber.
 11. Invention of claim 5 wherein said outlet is rotatablewithin said chamber.
 12. Invention of claim 4 wherein additional meansare provided connected to said chamber for exhausting the supplementalsupply of compressed gas therefrom.